18 research outputs found
Directed Cellular Self-Assembly to Fabricate Cell-Derived Tissue Rings for Biomechanical Analysis and Tissue Engineering
Each year, hundreds of thousands of patients undergo coronary artery bypass surgery in the United States.1 Approximately one third of these patients do not have suitable autologous donor vessels due to disease progression or previous harvest. The aim of vascular tissue engineering is to develop a suitable alternative source for these bypass grafts. In addition, engineered vascular tissue may prove valuable as living vascular models to study cardiovascular diseases. Several promising approaches to engineering blood vessels have been explored, with many recent studies focusing on development and analysis of cell-based methods.2-5 Herein, we present a method to rapidly self-assemble cells into 3D tissue rings that can be used in vitro to model vascular tissues
Targeted Delivery of Bioactive Molecules for Vascular Intervention and Tissue Engineering
Cardiovascular diseases are the leading cause of death in the United States. Treatment often requires surgical interventions to re-open occluded vessels, bypass severe occlusions, or stabilize aneurysms. Despite the short-term success of such interventions, many ultimately fail due to thrombosis or restenosis (following stent placement), or incomplete healing (such as after aneurysm coil placement). Bioactive molecules capable of modulating host tissue responses and preventing these complications have been identified, but systemic delivery is often harmful or ineffective. This review discusses the use of localized bioactive molecule delivery methods to enhance the long-term success of vascular interventions, such as drug-eluting stents and aneurysm coils, as well as nanoparticles for targeted molecule delivery. Vascular grafts in particular have poor patency in small diameter, high flow applications, such as coronary artery bypass grafting (CABG). Grafts fabricated from a variety of approaches may benefit from bioactive molecule incorporation to improve patency. Tissue engineering is an especially promising approach for vascular graft fabrication that may be conducive to incorporation of drugs or growth factors. Overall, localized and targeted delivery of bioactive molecules has shown promise for improving the outcomes of vascular interventions, with technologies such as drug-eluting stents showing excellent clinical success. However, many targeted vascular drug delivery systems have yet to reach the clinic. There is still a need to better optimize bioactive molecule release kinetics and identify synergistic biomolecule combinations before the clinical impact of these technologies can be realized
Growth-Factor-Releasing Polyelectrolyte Multilayer Films to Control the Cell Culture Environment
Polyelectrolyte multilayers
(PEMs) are of great interest as cell
culture surfaces because of their ability to modify topography and
surface energy and release biologically relevant molecules such as
growth factors. In this work, fibroblast growth factor 2 (FGF2) was
adsorbed directly onto polystyrene, plasma-treated polystyrene, and
glass surfaces with a poly(methacrylic acid) and poly-l-histidine
PEM assembled above it. Up to 14 ng/cm<sup>2</sup> of FGF2 could be
released from plasma-treated polystyrene surfaces over the course
of 7 days with an FGF2 solution concentration of 100 μg/mL applied
during the adsorption process. This release rate could be modulated
by adjusting the adsorption concentration, decreasing to as low as
2 ng/cm<sup>2</sup> total release over 7 days using a 12.5 μg/mL
FGF2 solution. The surface energy and roughness could also be regulated
using the adsorbed PEM. These properties were found to be substrate-
and first-layer-dependent, supporting current theories of PEM assembly.
When released, FGF2 from the PEMs was found to significantly enhance
fibroblast proliferation as compared to culture conditions without
FGF2. The results showed that growth factor release profiles and surface
properties are easily controllable through modification of the PEM
assembly steps and that these strategies can be effectively applied
to common cell culture surfaces to control the cell fate
Assembly of Tissue-Engineered Blood Vessels with Spatially Controlled Heterogeneities
Tissue-engineered human blood vessels may enable in vitro disease modeling and drug screening to accelerate advances in vascular medicine. Existing methods for tissue-engineered blood vessel (TEBV) fabrication create homogenous tubes not conducive to modeling the focal pathologies characteristic of certain vascular diseases. We developed a system for generating self-assembled human smooth muscle cell (SMC) ring units, which were fused together into TEBVs. The goal of this study was to assess the feasibility of modular assembly and fusion of ring building units to fabricate spatially controlled, heterogeneous tissue tubes. We first aimed to enhance fusion and reduce total culture time, and determined that reducing ring preculture duration improved tube fusion. Next, we incorporated electrospun polymer ring units onto tube ends as reinforced extensions, which allowed us to cannulate tubes after only 7 days of fusion, and culture tubes with luminal flow in a custom bioreactor. To create focal heterogeneities, we incorporated gelatin microspheres into select ring units during self-assembly, and fused these rings between ring units without microspheres. Cells within rings maintained their spatial position along tissue tubes after fusion. Because tubes fabricated from primary SMCs did not express contractile proteins, we also fabricated tubes from human mesenchymal stem cells, which expressed smooth muscle alpha actin and SM22-α. This work describes a platform approach for creating modular TEBVs with spatially defined structural heterogeneities, which may ultimately be applied to mimic focal diseases such as intimal hyperplasia or aneurysm
Engineered Test Tissues: A Model for Quantifying the Effects of Cryopreservation Parameters
Engineered tissues are showing promise as implants to
repair or
replace damaged tissues in vivo or as in vitro tools to discover new
therapies. A major challenge of the tissue engineering field is the
sample preservation and storage until their transport and desired
use. To successfully cryopreserve tissue, its viability, structure,
and function must be retained post-thaw. The outcome of cryopreservation
is impacted by several parameters, including the cryopreserving agent
(CPA) utilized, the cooling rate, and the storage temperature. Although
a number of CPAs are commercially available for cell cryopreservation,
there are few CPAs designed specifically for tissue cryostorage and
recovery. In this study, we present a flexible, relatively high-throughput
method that utilizes engineered tissue rings as test tissues for screening
the commercially available CPAs and cryopreservation parameters. Engineered
test tissues can be fabricated with low batch-to-batch variability
and characteristic morphology due to their endogenous extracellular
matrix, and they have mechanical properties and a ring format suitable
for testing with standard methods. The tissues were grown for 7 days
in standard 48-well plates and cryopreserved in standard cryovials.
The method allowed for the quantification of metabolic recovery, tissue
apoptosis/necrosis, morphology, and mechanical properties. In addition
to establishing the method, we tested different CPA formulations,
freezing rates, and freezing points. Our proposed method enables timely
preliminary screening of CPA formulations and cryopreservation parameters
that may improve the storage of engineered tissues